Flame controlled system



Oct. 4, 1932. 5, DEN|$QN 1,880,871

FLAME CONTRQLLED SYSTEM Fil ed Dec. 4, 1930 INVENTOR F REDERIOKS.DENISON ATTORNEYS Patented Oct. 4, 1932 UNITED STATES PATENT? OFF-ICEFREDERICK S, DENISON' OF'HINNEAPOLIS, MINNESOTA, ASSIGNOR- TOMINNEAPOLIS- "'HONEYWELL REGULATOR OOMPANY, 0F MINNEAPOLIS, MINNESOTA,A. CORPORA- '1ION OF DELAWARE m CONTROLLED SYSTEM Application filedDecember 4, 1930. Serial No. 499,993

This invention relates to a control system including a flame source andan electric circuit, th energization 'of which circuit de-- pends u onthe passage of current by the gas flame; that is, the circuit cannot becompleted except through the elements of the flame. The invention hasfound valuable application as a device for interrupting fuel supply to afuel burner in. case of pilot flame extinguishment, and provides meanscontrolled by the pilot flame and which is not adversely affectedbyambient temperatures such as burner temperatures In devices where apilot flame is depended upon to ig nite a burner, and in which it isdesired to discontinue fuel supply to the burner if the pilot flame isextinguished, it is the practice to use a bimetallic or equivalentthermal memher, as an element in a system for controlling fuel supply tothe burner. This metallic hermal member, as a switch control element,

is so placed as to be exposed both to pilot and furnace heat. Underthese conditions, the metal becomes overheated and is moved such adegree that on cessation of pilot flame, an appreciable period of timeelapses before it canaifect its switch-closing function, to interru ptfuel feed as by closure of a valve. Therefore, fuel continues to besupplied, a great quantity is wasted and often explosion results when iition is attempted.

It is, there ore, an important object of the present invention to use ameans for im mediately discontinuing fuel supply on pilot flameextinguishment, and to accomplish this result withoutthe useofthermostatic inetal and ,to provide a device which unfailinglyopcrates and is not liable to become inoperative "as the result of thelarge temperature overruns, as when exposed to main burner tem-'peratures. Most safety pilots have operated upon the thermostaticprinciple and have therefore had, in order to be successful, to becompensated against furnace temperatures,

. or unless this was done their response was not dependable. The presentinvention uti- -'lizes a grid-glow-tube'as part of the control furnace."The tube is operable to permit pasto control the circuit through thesecondary v system and ina manner to beentirely independent of theamount of heat present 1n the sage of current, and opening of the fuelvalve only when the circuit is completed by actual contact of the pilotflame with a conducting element of the circuit. This is a valuablefeature.

The invention is diagrammatically represented in the single figure ofthe drawing and in said drawing: The numeral 10 indicates a burner, andthe numeral 9 a fuel supply line for the burner. In the fuel line 9 isan electrically operable valve 7, including a movable valve element 5controlling the flow orifice 8. The element 5 is connected to the core 3of a solenoid, the coil of which is indicated at i. Electricallyoperable means is provided for controlling the solenoid and, in thisinstance, comprises arelay, the coil of which is indicated at 31. Thisrelay controls a contact which is connected by conductor 36 with the hotline 1. The other side of this contact is connected by conductor 40 withone termi; nal of the coil 4:, and the opposite side of the coil isconnected by conductor 41 with the ground side 2 of the power line. Apilot device for the burner is indicated at 12 and the supply pipe forthis pilot device is indicated at 13. The pilot flame, for convenience,is indicated at 15.

A transformer is indicated at A and'comprimary 53 and a secondaryelement 56. A

grid-glow-tube is employed, the anode being.

indicated at 22, the grid at 46 and the cathode at 33. Connectionsacross the power line include in series therein, the primaries of thetransformer and choke coil. These connections include conductor 51 fromthe ground transformer, line-52 "connecting the opposite terminal ofthis primary with the primary of the choke coil, the opposite terminalof the primary of the choke coil being connected by conductor 54 withthe hotline 1.

Means is also provided for alternately energizing anddel-energizing thechoke coil and, therefore, varying the electrical effects in thetransformer. In this instance, a heat-affectable device, such as aroomthermostat, is used line to one terminal'of the primary of the 1 Ielement R and two contacts B and W. The

contact W is connected by conductor 59 with one terminal of thesecondary of the choke coil, the opposite terminal of this secondarybeing connected by conductor 57 with contact B. Contact W is firstclosed, and then contact B. A holding circuit is provided which isdependent on closure of contact 61 controlled by relay'coil 81. Contact61 is connected by conductor 60 with R of the room thermostat, and aconductor 62 connects the opposite side of this contact 61 with theconductor 57. After closure of 61 the secondary of the choke coil willnot be de-energized after contact B is opened, the current being underthese conditions maintained through contact W until opened by continuedheating of the element R. The foregoing is only one of many means whichcan be used for varying the electrical effects of the transformer. Thechoke coil is used because only low voltage is required, and thus arcingand possible fusing of the thermostat contacts is prevented. A relaycontrol circuit includes therein, in series, the secondary 27 of thetransformer, relay coil 31, and the anode and cathode of thegrid-glow-tube, and includes conductor 30 connecting one terminal of thesecondary with one terminal of the coil 31, conductor 32 connecting theopposite end of the relay coil with the cathode 33, conductor 21connecting the anode 22 with conductor 26 which latter conductorconnects with the opposite side of the secondary of the transformer.

A grid circuit includes an electrode 16, in this instance formed of analloy of nickel and iron, as means adapted to be impinged by the pilotflame to close the grid circuit. The grid circuit includes this element16; conductor 18 connected to conductor 45 which latter conductor isconnected with the grid 46; and ground connections 70 and 71respectively from the ground line, and from the fuel supply pipe 13. Abranch connection 20 is provided between the flame impingeable means 16and the anode. This connection 20' has therein a condenser 19.- Theelectrical characteristics of the tube and'transformer are such thatcurrent sufficient to close the relay is only passed by the tube whenflame is present and when the choke coil circuit is closed. This is morethoroughly explained herebelow. The condenser in the branch 20 is inseries with he anode and grid and is also in series with the electrodeand one terminal of the secondary of the transformer.

Operation Let it be first assumed that there is no flame. Under theseconditions the condenser 19 is affecting the grid 46 in a manner toprevent passage of current between anode and cathode and therefore relay31 could not be closed on closure of the thermostat at BW. It will beunderstood that the duty of condenser 19 is to charge the grid when nocurrent is in the flame-electrode branch of the grid circuit.

Now assume the pilot to be lighted. The grid-electrode circuit isaffected to cause condenser leakage suflicient to overcome thegrid-charging effect of the condenser, and condition the tube forpassage of current. However, at this time the electrical effects are notsuch as to energize relay 31. On closure at BW, the secondary 56 of thechoke coil is shorted, and voltage is reduced in coil 53, increased incoil 50, and increased in coil 27 so that the combined effects of gridand transformer are sufficient to energize coil 31 of the relay, closethe relay and open the fuel valve. If, however, the pilot flame 15 isextinguished (and the flame-electrode circuit therefore broken) and if,during this period, a call for heat is made at the thermostat, noenergization of relay coil 31 is possible because it is only by thecombined action of the flame-electrode and the transformer circuits thatthis energization can be accomplished.

It will be noted that, what may be termed, a valving action is performedby the choke coil and grid-glow-tube. When both valves are properlyopen, suflicient'current can pass to energize the relay. When either isclosed, the other cannot effect sufiicient energization of the relay toclose it. The open-valve action of the grid-glow-tube is dependent onproper electrical efi'ects appear in the sec-- ondary and when flame ispresent, the gridglow-tube passes suflicient current to close the relayor equivalent device. A very small amount of current passes through theflame, which ishighly resistant. The amount of current capable ofpassing is unable to affect any but a very sensitive electricalinstrument, which the grid-glow-tube is. The very small current passedby the flame is utilized for conditioning the tube to pass current, sothat as soon as the room thermostat or equivalent control deviceoperates to properly affeet the transformer, the relay is closed.

In the presence of flame, that is as soon as the flame 15 contacts theelectrode 16, the grid charge is so affected as to condition the tube topass suflicient current to close the When the current in the circuit isoper ative, enough leakage ta es place to overcome thegrld-chargingefiect of the condenser, to condition the tube to passcurrent on a call for heat by the [room thermostat, at

which time the secondary of the choke coil H circuit is closed. 7

The broad feature of this invention is the control by use of the flameas circuit maker and breaker.

I claim as my invention:

1. A control system for a burner including a low voltage circuit, a roomthermostat controlling the low voltage circuit, an electrical- 1yoperated burner control device, a medium voltage circuit for energizinvice, a grid-glow-tube, a big voltage circuit including therein theanode and cathode of the grid-glow-tube, a grid c'ircuitincluding anelement adapted to be impinged by flame to complete the same, I'neansassociated with the room thermostat and-low voltage circuit forcontrolling the current flow through said high voltage circuit, andmeans associated with said high voltage circuit for controlling the flowof current through .said -medium voltage circuit thereby to control theoperav tion of said burner control device;

2. A control system for a burner including a low voltage circuit, astep-down transform-. .er therefor, a room thermostat controll ng thelow voltage-secondary thereof, an elec- I -trically operated burnercontrol device, a

medium voltage circuit for energizing the control device, agrid-glow-tuhe, a step-up transformer havin its primary in series withthe primary 0 the first mentioned stepdown transformer and having itssecondary ina high voltage circuit including therein the anode andcathode of the grid-glow tube a grid circuit includingan element adaptedto be impinged by flame to complete the same,

and means in the secondary circuit of the step-up transformer to controlthe circuit of the burner control device, said room thermostat servingto controlthe operative energiaation of the'step-up'transformer b shortC11- my hand cuiting the secondary of the stepown transformer'. 1

In witness whereofyIhave hereunto set this-28th day of November, 1930.

' FREDERICK S. DENISON;

the control de-

